Rotary compressor



Sept. 2, 1941. DICK ETAL 2,254,938

' ROTARY COMPRESSOR Filed July 10, 1939 no.2. I

BURNS DICK" FRED l -LSTROUP- ATTORNEY INVENTORS Patented .Sept. 2, 1941 ROTARY COMPRESSOR Burns Dick, Ferguson, and Fred H. Stroup, Kirkwood, Mo., assignors to Wagner Electric Corporation, St. Louis, Mo., a corporation of Delaware Application July 10, 1939, Serial'No. 283,612 p 5 Claims.

Our invention relates to rotary compressors and more particularly to an improved stator construction therefor.

One of the objects of our invention is to so construct a rotary compressor that it will be properly lubricated at both low and high speeds out will not blow oil out of the intake at lower speeds when the pressure in the receiver of the compressor is high.

Another object of our invention isto provide the stator of the compressor with grooves which are so associated with the inlet and outlet openings that the compressor will operate more efiiciently. V

Other objects will become apparent from the following description taken in connection with the accompanying drawing in which Figure 1 is a side view of a rotary compressor embodying our invention, said compressor being shown with an end plate removed; Figure 2 is a view of onehalf of the stator surface which cooperates with the rotor blades and shows the grooves therein associated with the outlet port of the compressor; Figure 3 is a side View of a portion of the stator taken on the line 3-3 of Figure 2; and Figure 4 is a view of the other half of the stator surface which cooperates with the rotor blades, showing the grooves therein associated with the inlet port.

Referring to the drawing in detail, numeral l indicates the stator of a rotary compressor in which is a rotor 2 secured to a shaft 3 eccentrically mounted in the end plates 4 and 5 (Figures 2 and 4). The rotor is provided with a plurality of slots 6 in which are reciprocably mounted blades 1 for cooperation with the inner surface of the stator to perform the compressing operation in a well-known manner. The end plate 5 is provided with an inlet port 8 and the end plate 4 is provided with a discharge port degrees in a clockwise direction from this close point. By this arrangement it is seen that as the rotor rotates, ea ch blade traps the air or other fluid which enters the chamber ahead of the blade as the blade passes the inlet port and this air will be compressed and forced out of the keyway l3 in the rotor.

the discharge port as the blade approaches this port. w

The relatively moving parts ofthe compressor are all freely lubricated with oil, which oil may be suppliedthroughthe shaft 3 from an oil dome or oil reservoir by means of an axial passage II and a cross passage 12 which communicates with The oil dome is generally adjacent the end plate 4 and the compressed air is forced out of the discharge port into the oil dome and from there admitted to the storage tank." Thus the oil in the dome is always under'pressure thereby causing the oil to be forced through passage I I. In compressors which are constructed to operate at variable speeds, the amount of oil fed to the compressor varies with the speed. While the amount of Oil per minute increases with the speed, the quantity of oil per revolution really decreases. At low speeds and high dome pressures less oil is pumped by the compressor back into'the dome since the pumping must be done against the high pressure in the dome. The same condition would be present athigh speeds if the pressure in the dome'were permitted to rise high enough, say to the stalling point of the compressor. In practice, however, the condition at high speeds is not obtained because the compressor is shut off before the stalling point 'is reached. It is thus seen that in the final analysis, the residue of oil in the compressor at low speeds and high dome pressure is greater than at high speed and it is the purpose of our invention to so construct the compressor that no undesirable conditions will be present because of this residue of oil.

Since the discharge port of the compressor is positioned at a point which is spaced in a clockwise direction from the close point I0,.there will be a small chamber between this port and the close point in which air and oil can be trapped after the blade passes the discharge port. This trapped air and oil will be compressed as the blade approaches the close point and will be forced through the close point if no means 15 employed to relieve it. Such a condition results in what is known as a compressor knock.

In accordance with one feature of our invention, we provide means for permitting compressed fluid to by-pass the blade and enter the chamber behind the blade after said blade has passed the discharge port, thus preventing compression of the air and oil after the discharge port has been passed. The inner surface M of the stator adjacent the discharge port 9 of the backing plate 55 4 is provided with a recess I5 and communicating with this recess is a circumferentially extending groove I6 which extends to a point closely adjacent the close point ill but does not extend beyond this point. With this construction it is seen that when a blade passes the discharge port 9, there will continue to be communication between the discharge port and the chamber ahead of the blade until the blade reaches the close point Hl. Thus the air and the oil which is being compressed ahead of the blade is free to by-pass the blade by means of the circumferentially extending groove l6 and thus enter the chamber behind the blade and passiout of the discharge port 9 which is shown as controlled by a check valve l8.

We have discovered that this circumferentially extending groove l6 operates efficiently to eliminate the so-called compressor knock but its use apparently causes an end thrust on the blade which results from thecompressed air and oil ahead of the blade flowing toward the groove Hi. This end thrust creates an undesirable wear on the end plate 4 adjacent the groove [6. In order to eliminate this end thrust, we provide a second circumferential groove IT in the surface it of the stator, which groove is at the opposite end of the stator. This groove is .a substantial duplicate of the circumferentially extending groove i6 and extends from a point axially opposite the point where the blade passes the recess l5 and to a point closely adjacent the close point I0. Because of this groove H, the air and oil which is being compressed by the blade after it passes the discharge port, will now by-pass the blade at both ends of the blade and there will be no end thrust set upsince the force caused by the flow of the air and the oil toward one groove will be counter-acted by theforce caused by the flow of the air and the oil toward the other groove. I

In order that the chamber at the rear of the blade after passing the close point l may be charged with air under atmospheric pressure before the blade passes the inlet port 8, it has been the practice to provide a groove which extends from the inlet port toward the close point. This groove in prior practice has been either in the end plate which is provided with the inlet port or in the stator surface adjacent the end plate provided with said inlet port. Such a groove has been found to function properly to pre-load the blade and thus increase the efllciency of the compressor, but it has been discovered that during low rotor speed, when the compressor contains a greater amount of oil, the oil collecting in this groove will be blown out through the inlet port (due to the groove connecting directly with the inlet) when the blade passes the rearward 'end of the groove and places the chamber at the rear of the blade in communication with the inlet port. This undesirable blow back" of oil at low speed is caused by superatmospheric pressure of fluid in the chamber behind the blade after it passes the close point instead of a suction as is the condition at high speeds. This super-atmospheric pressure is the-result of the receiver being at substantially maximum pressure and air cannot be readily forced out of the discharge port so it is forced by the close point during the slow movement of the blade.

We discovered that this blow back of oil to the inlet at low speeds and when the receiver pressure is high can be eliminated and the func- I tion of the pre-loading groove retained. This is accomplished by eliminating the groove adjacent the inlet port and providing a groove 19 on the opposite side of the end of the compresso r opposite .the inlet port and in the surface M of the stator. This groove, as shown in Figure 4, extends from a point axially opposite the inlet port and toward the close point ill of the compressor. The length of thegroove is preferably such as to'extend over an angle of substantially degrees on the surface of the stator. With this groove positioned as shown, it is seen that when the compressor is operating at low speeds and there is a super-atmospheric pressure behind the blade at the time it passes the end of the groove, the oil which is blown out of the groove by the lay-passing of air from the rear of the blade to the chamber ahead will be blown into this chamber at a point remote from the inlet and not directly into the inlet and, therefore, because of this, the oil laden air will be expanded in the chamber and not reach the inlet before the inlet is cut off. Thus groove ISfunctions to permit pre-loading of the blades when the compressor is operating at high speeds but because of its location, the objectionable blow back of oil through the inlet port is prevented at low speeds when the compressed airin the receiver is at a high pressure.

Being aware of the possibility of modifications in the particular structure herein described withoutdeparting from the fundamental principles of our invention, we do not intend that its scope be limited except as set forth by the appended claims.

Having fully described our invention, what we claim as new and desire to secure by Letters Patent of the United States is:

1. In a rotary air compressor having its movable parts lubricated by oil and capable of compressing air and forcing it into a receiver against air pressure therein, said compressor comprising a stator having a chamber therein, a rotor eccentrically mounted for rotation within said chamber in close proximity to the wall of said chamber at one point to form a close point therewith and provided with blades for cooperation with the inner surface of the stator, means for rotating said rotor, end plates for the stator closing said chamber, one of said end plates being provided with the sole inlet port for the compressor and the other end plate with the sole outlet port for the compressor, both said ports being positioned adjacent the inner surface of the stator at opposite sides of said close point, said outlet port being spaced circumferentially rearward from the close point of the rotor and stator, and means comprising circumferentially extending grooves in the stator surface for permitting fluid under pressure to'pass a rotor blade after said blade has passed the outlet port, one of said grooves being at the outlet end of the stator with its rearward end communicating directly with the outlet port and its other end closely adjacent,

the close point, said other groove being at the opposite end of the stator with its rearward end substantially in axial alignment with the rearward end of the first groove and its other end closely adjacent the close point.

2. In a rotary air compressor having its movable parts lubricated by oil and capable of compressing air and forcing it into a receiver against air pressure therein, said compressor comprising a stator having a chamber therein, a rotor eccentric'ally mountedfor" rotation within said chamber in close proximity to the wall of said chamber at one point to form a close point therewith and provided with blades for cooperation with the inner surface of the stator, means for rotating said rotor, end plates for the stator closing said chamber, said compressor being provided with a single inlet port and a single outlet port both adjacent the inner surface of the stator at opposite sides of said close point, said outlet port being in one end plate and spaced circumferentially rearward from the close point of the rotor and the stator, and means comprising two circumferentially extending grooves for permitting fluid under pressure to pass a rotor blade after said blade has passed the outlet port, one of said grooves being at the outlet end of the stator with 3. In a rotary air compressor having its mov able parts lubricated by oil and capable of compressing air and forcing it into a receiver against air pressure therein, said compressor comprising a stator having a chamber therein, a rotor eccentrically mounted for rotation within said chamber in close proximity to the wall of said chamber at one point to form a close point therewith and provided with blades for cooperation with the inner surface of the stator, means for rotating said rotor, end plates for the stator closing'said chamber, said compressor being provided with a single inlet port and an outlet port both adjacent the inner surface of the'stator at opposite sides of said close point, said inlet port being at one end of the stator and spaced circumferentially forward of the close point of the rotor and the stator, and means comprising a single circumferentially extending groove associated with the inlet port, said groove being at the end of the stator opposite the inlet port and extending rearwardly a substantial distance toward the close point and from a point in axial alignment with the inlet port.

4. In a rotary aircompressor having its movable parts lubricated by oil and capable of com pressing air and forcing it into a receiver against air pressure therein, said compressor comprising a stator having a chamber therein, a rotor eccentrically mounted for rotation within said chamber in close proximity to the wall of said chamber at one point to form a close'point therewith and provided withblades for cooperation with the inner surface of the stator, means for rotating said rotor, end plates for the stator closing said chamber, said compressor being provided with a single inlet port and an outlet port both adjacent the inner surface of the stator at oppositesides of said close point, said inlet port being in one end plate and spaced circumferentially forward of the close point of the rotor and the stator, and means forming a single circumferentially extending groove in the stator adjacent the end plate which is opposite the end plate that is provided with the inlet for permitting fluid to enter the chamber behind a blade prior to the blade passing the inlet, said groove extending over a substantial arc toward the close point and from a point in axial alignment with the inlet port.

5. In a rotary air compressor having its movable parts lubricated by oil and capable of compressing air and forcing it into a receiver against air pressure therein, said compressor comprising a stator having a chamber therein, a rotor eccentrically mounted for rotation within said chamber in close proximity to the wall of said chamber at one point to form a close point therewith and provided with blades for cooperation with the inner surface of the stator, means for rotating said rotor, end plates for the stator closing said chamber, one of said end plates being provided with an inlet port only and the other with an outlet port only, both of said ports being positioned adjacent the inner surface of the stator on opposite sides of said close point, said outlet port being spaced circumferentially from the close point of the rotor and the stator, means comprising circumferentially extending grooves in the stator surface for permitting fluid under pressure to pass a rotor blade after said blade has passed the outlet port, one of said grooves being at the outlet end of the stator with its rearward end communicating directly with the outlet port and its other end closely adjacent the close point, said other groove being at the opposite the inlet port and extending rearwardly from with the inlet port. BURNS DICK. FRED H. STROUP.

a point in axial alignment 

